sex after scuba diving?!

i went scuba diving a few weeks ago. i just got home about a week ago, and my girl greeted me at the mall when i got back. well she was happy that i was back so we decided to go to the bathroom near the empty part of the mall... you can guess what happened next. so as me and her where getting to it i felt this strange crawling type feel in my penis, almost like a night crawler the size of a guitar string was wriggling up me penis from base to just where the head starts and making little patterns and stuff. i haven't gone to the doctor yet... im freaking out, PLEAS HELP!